47-55.1 1951 GMC Floor High Hump

[cff]

I have a 1951 GMC half-ton with a 3 on the tree. If the truck had a 4-speed in it,would it have had a high hump on the floor for clearance or would it have fit under the flat floor panel? And if it had a high hump, can you buy it from an aftermarket supplier or do you have to find an original one? Thanks, Ron

[joedoh]

the only tall hump was a COE. the 4 spd floor mount on conventional cabs just has a small bump where the shifter comes through. both the 3 spd and 4 spd covers are available at any aftermarket source, I like bowtiebits.com

https://www.bowtiebits.com/store/store_product_detail.cfm?Product_ID=3262

[Tempest67]

I made mine using the center piece of the floor for the base.

sorry, this is the best pic I can find, but you can see the flange I made to attach to the firewall/toe board

[mr48chev]

Those 4 speed transmission covers barely have enough room to clear the shift mechanism in the trans. They might give you a little room on top of a T 5 but aren't going to help with an automatic.

Most do something similar to what Tempest67 did on his and each one is a bit different than everyone elses because the needs are a bit different. just don't make the hump bigger than what you need in the area of the gas pedal. I've driven a couple of hot rods that the builder forgot that they needed to be able to operate a gas pedal somewhat comfortably and totally missed the mark.

[cff]

Thanks guys. Great info

[cff]

Will the 4-speed from a 64 chevy half ton fit ok? I'm putting in a 64 292 and rear end, so I won't have the torque tube setup.

[dsraven]

if you're installing the 292 and the 4 spd from the same donor truck, '64, then it will likely have the granny low gear. most guys simply start in 2nd with those unless they have a load. possibly you could find a newer trans with better ratios or even an overdrive to help with rpm's on the highway. be mindfull of the rear axle ratio and the trans ratios with the 6 cyl engine. I guess it would be just like driving the '64 as far as highway speeds and power are concerned. lots of those guys are looking to upgrade to a 5 spd. it depends on what you want.
you probably know this already but in case you don't, the installation of an open driveline in place of the old torque tube will require an adapter at the axle to spring mount because the torque tube axles had a pivot on the spring mount and weren't mounted directly on the center of the axle tube like the open drivelines are. they sell those adapters at some of the suppiers. some guys make their own using spring pads from a trailer axle supply place.

[dsraven]

here is a link to a video that shows installing an s10 rear axle into an AD truck. it has some good info and a how to on the whole thing, including relocating the axle center line to the correct place. they make their own adapter. I would use something other than a nut welded onto the adapter plate or do something like drill through the plate, slip a short length of round bar half way into the hole, and plug weld from the back side so you could grind it smooth and the round bar protruding from the top side would be a good fit in the axle bracket with no welding protruding on the top side. then when its all assembled and bolted up weld the bracket to the spring pad.
one thing to remember when grinding and welding on axle tubes is to keep the amount of heat to a minimum. axle tubes can be bent from the heat applied to only one side of the tube. trust me on this. I have had to repair a few home done jobs. usually it means getting another rearend.
https://www.google.ca/url?sa=t&sourc...AiiNoLjfG9EHlL

here is a link that shows the rear axle conversion kit that is supposed to work with the open driveline conversion. if you do make your own it is a matter of getting the hole in the axle spring pad in the correct spot so the axle lines up in the fender opening correctly. personally, I like to mark the axle at the centerline of the spring perches, then assemble it all without welding the perches on yet. do the u bolts up just enough to keep it all assembled and in place. then do the driveline angles and check centering before tack welding the perches to the axle. then take it all down and do a good weld on the perches to the axle. that way there are no "oopsies". you need to have the truck weight on the spring as well. like a simulated ride height. you will also need to make up some shock mounts at some point.
welders series has lots of fabrication brackets etc. their parts are quality and they are Canadian so shipping is pretty quick.
https://welderseries.com/?_vsrefdom=...waArqbEALw_wcB

[MD2020]

My 56 had a high hump with a lot of holes in it so I bought a repop and it was flat but works good with clearance, 350 small block with Muncie 22 4 speed, I only had to cut a hole for the shifter stick.
BUT I have a Fatman chassis so they could have moved everything

[dsraven]

you may also look at the full syncro 3 speed trans if you don't wanna mess up your floor. I think it would bolt up to your bellhousing and you could use the column shifter-or a floor shifter if that what you want. Ihear some guys are using the S10 5 spd with the inline 6 as well.
some good info in this thread too.
http://67-72chevytrucks.com/vboard/s...d.php?t=795406

[dsraven]

sorry, got down a rabbot hole there.
I am with tempest, install the driveline and fab a new floor plate using the old one as a perimeter template. use a bouble thick edge for strength if you want, just to keep things from bending around the bolt holes. rivet nuts work great to keep them held down and still be able to remove the floor plate if needed.

[leegreen]

Hi CFF, nice to see another local on the forum.

There are a bunch of ways to fit a newer rearend. if memory recalls swapping to the '64 springs is one of them as the length is similar - but check the width at the eyes too.
You should be able to re-use the 51 springs if you take the spring packs apart, take the top two leafs, and reverse them front to back. Or do the adapter thing dsraven describes.

I assume you want to ditch the 3 speed and closed drive to get higher gears, as already suggested make sure the rear end ratio on that '64 is one that gets you what you want. Any GMC rear axle from a half ton up to like '68-69 should be the right width.

The '64 trans will most likely drive like a 3 speed but with a granny low you will never use. And 1:1 final drive.
I think the '64 292 and bellhousing should be easy bolt up to the '51 clutch linkage but I have not done this myself. The 292 is longer than 216/235, you may need to look for shorter waterpump or switch to electric rad fan. Since you are going to be fabbing engine and trans mounts I'd put the engine and trans in and get it all in place and radiator clearance sorted before worrying too much about the trans hump. You should not need much of a hump

For overdrive options, the t5 will work. Look for lugnutz web page on t5 swaps. I have a '93 s10 t5 behind a 250 in my '52, it is pretty easy. you will need an adapter from smaller trans centre bore to truck bellhousing that is also a spacer to deal with the input shaft length. hotrodworks is where I went and it works perfectly. And a safari van 11" clutch disk. But the 64 bell, PP, release bearing should all be OK. The cost of this can add up, T5s are going for a lot more than they used to, the adapter and clutch disk come from the states and are expensiveish once you get them across the 49.
A NV3500 is also an option and I think you can do that with just a different clutch disk. Nv3500 is a stronger trans but in my experience drives more like a truck trans, the t5 is nicer shifting. Either is strong enough for the 292 or a small v8.

[chevyguyase]

Sounds like leegreen and I are on the same page. I'm running a '54 chev. 3100, 250 eng, T5 trans and astro van 11 inch clutch. My floor is flat and I have plenty of room under the trans cover. I took a granny gear 4 speed out of it and modified the cover so it would be flat. I'm running a 3.46 ratio, 10 bolt rear axle, which works perfect for me. You're not constantly shifting from 5th to 4th on inclines. If you go this route make sure the 5th gear is around .70 to 1. The 4 cyl versions of these t5s are .90 to 1. 4th and 5th gear are almost the same.

[dsraven]

as a heads up, some guys put the rad in front of the rad support to gain a little room.

is the '64 rear suspension not a trailing arm suspension? my '63 gmc was trailing arm with coil springs. pretty good ride, no wheel hop to speak of if doing a burn out (well, as much of a burn out as you can with a stock 283, haha). coil springs maybe have less weight carrying ability. I installed variable rate springs for a good ride with no load but able to carry some weight once the soft part of the springs was overcome. I guess that doesn't matter too much since you would cut all the brackets off anyway, or swap in the whole rear suspension for an added bonus of a lot more work. lol.
here is an rpm calculator if you wanna find out what you rpm will be on the highway or any given trans gear
https://spicerparts.com/calculators/...rpm-calculator

and another
https://www.randysworldwide.com/calc...sion-ratio-rpm

and a last one
https://www.tremec.com/calculadora.php

[dsraven]

here is a copy and paste from another post on this site about the 292 and hp-torque ant different rpm's.


1966 sales data book shows 170 gross HP @ 4000, 153 net@ 3600, and 255 net lb ft @ 2400 with torque peak almost equal @ 1600, so it's got a good range . So gear it to do what you want .

[leegreen]

I thought Chevrolet had the trailing arm and GMC was leaf, but any combination is possible given different factories and specifications and the fact that many of these trucks have already been rejuvenated a time or two by now.

With a '52 shortbox on a trailing arm frame, the stock c10 springs don't even begin to compress and it sits way high. Springs from a late 60s early 70s chevelle will bolt right in and are a lot softer. my current set is from a chevelle wagon which seems about right, it sits low and can still have some weight in the bed.
Full disclosure, my '52 is on a '65 trailing arm frame because s10s hadn't been invented and mustang IIs were worth new car prices when I started this project. I'll do a build thread someday once I have some miles on it and can say something useful about how well it works

[dsraven]

LG, good info. my truck was a 63 GMC and it had an inline 6 and 3 on the tree originally. somewhere along the way somebody upgraded to a 283 with a hurst floor shifter on the original non syncro 3 spd. I found the floor shifter a pain because it was a short handle so it was at about the height of the bench seat. it had trailing arm suspension with drums all around. I used it as a daily driver and used to haul sleds, dirt bikes, dunebuggies, bicycles and firewood (as a kid we heated our house with an antique wood furnace in the basement and I was the wood guy). My tryck had an 8 ft box and I used to cut 10 ft lengths of wood and stack it in the box as high as the cab roof, then drive DOWN the mountain in the shuswap area of B.C. yeah, I know what brake fade is, lol. anyway, the point is the old truck had the guts to do that with the Moog variable rate springs installed, and it rode pretty well on the road normally with no load. it cruised down the highway at 60 mph but that was wrung out like a wet sponge if I remember correctly. don't know what axle ratio it had. it would do a burn out if pushed, hard, lol.
thats why I suggest to figure out what the driving conditions will be and then figure out what axle ratio and trans ratio's will result in the best fit for the old 6.

[dsraven]

after running some numbers on the rpm calculator I assume the rear axle ratio was somewhere around the 4.10/1 ratio. wrung out like a wet sponge was really only about 3 k rpm, it just seemed like it was wrung out like a wet sponge, lol. I guess some sound deadener would have been an asset. haha.

[mr48chev]

Originally Posted by cff

Will the 4-speed from a 64 chevy half ton fit ok? I'm putting in a 64 292 and rear end, so I won't have the torque tube setup.

It will bolt right in and still be an SM 420 just with open drive. Same trans with different tail shaft and extension housing.

SM 420 ran from 47 to 67 and SM 465 started in 68 and ran through 91.

[cff]

The 292 block measures 2" shorter than the 228 that it came with, so I was thinking that the length maybe wouldn't be a problem unless the water pump and fan/pulley array is longer than normal. I was going to use a full syncro 3 speed, but the 228 bell housing is totally different and there's no way it will bolt to the 292. And the 3 on the tree linkage bolts to the bell housing on the 228, but it won't bolt to the 292(1964) bell housing. I don't know if the linkage on a 51 chevy bolted to the bell housing but I don't have an early 50's bell housing to check. I would like the interior to look original and don't want a 3 speed shifter on the floor, that's why I figured i would go with the 4 speed from the 64. It would look stock and I know it's a granny 1st gear' but I don't mind. I've driven a lot of those old 4-speeds. I plan on using the truck as a daily driver and work truck. It has a 7 foot box. At least during the decent weather, and plan on hauling what it can handle. Don't plan on lowering it. The 64 rear end has 3.08 gears in it. I do have to cut the trailing arms off and weld on a couple spring purchases and thanks to joedoh on where I can buy that 4-speed hump and dsraven for the vids. And to everyone actually for your input. If someone knows how I can use the original 3 on the tree from the gmc in a chevy without the gmc bell housing I would appreciate it. I haven't bought the 4-speed hump yet. I'll post a pic or 2, if I can figure out how.

[cff]

PS. LEEGREEN. I sent you a PM

[cff]

A couple pics I have. The front end is off it now

[dsraven]

too bad about your shop. beimg full of old truck junk. let me know if you need a hand cleanng it out.....
haha, looks awesome.

[dsraven]

are you transplanting the old truck onto the newer frame or just swapping the required parts over? personally, I might look into the frame swap, install some disc brakes and power steering (not that tough since the square body stuff is sorta compatible). winner either way.
keep posting pics, us Canucks need a little motivation in the winter sometimes, lol.

[cff]

Hi. No I'm just putting in the 292 and one of the trannies. I just want to use it as a work truck and do it as cheap as possible. I do want it to be dependable. I would like to drive it to Quesnel and maybe Edmonton. I think it should be ok with 3.08's. I plan on replacing all wheel bearings, brake and fuel lines, tires obviously. And whatever else I need to. I got it 22 years ago from Yakima and bit's been inside the whole time. Not a rust hole anywhere's. There's some 10 or 12 inch wood sides that go on the top sides of the box. I just took them off while I was washing the dust off of it.